1. Field of the Invention
The present invention relates to a stringing preventing member and an injection molding apparatus.
2. Description of Related Art
As described in JP-A-2001-225359, it is known that in an injection molding, when separating a molded article from molten resin within an injection molding nozzle, the resin is not cut completely from the molded article to cause stringing. When the stringing arises, it is necessary to cut a string at the time of taking out the molded article from a mold. Further, the treatment of the molded article becomes troublesome due to the string thus generated. JP-A-2001-225359 discloses a technique that the stringing can be prevented by improving the shape of the opening at the tip end of the injection molding nozzle.
Further, JP-A-2004-188951 describes a technique in which a circular concave portion is provided at the resin injection port of a spool bush adhered to the tip end of an injection molding nozzle to cause the solidification of the resin thereby to prevent the stringing.
However, according to the method described in JP-A-2001-225359, since it is necessary to process the injection molding nozzle itself, a user of the injection molding apparatus is required to specially order the manufacturer of the injection molding apparatus to process the apparatus. Thus, since the cost of the injection molding apparatus rises and the delivery period of the apparatus becomes longer, the convenience for a user degrades. Further, since the generation condition of the stringing differs depending on the resin material and the molding condition (temperature, injection pressure etc.), it is difficult to prevent the generation of the stringing in accordance with the change of the material and the molding condition by the method of processing the injection molding nozzle itself. Thus, it is desired on the user side of the injection molding apparatus to prevent the generation of the stringing in a manner that the injection molding nozzle as a functional portion of the main body of the injection molding apparatus is used as it is, then a member for preventing the generation of the stringing is prepared on the user side without depending on the manufacturer of the injection molding apparatus, and the member is exchanged in accordance with the material and the molding condition.
Further, according to the method described in JP-A-2004-188951, since a reservoir (concave portion) for the resin is provided at the tip end of the injection molding nozzle, the resin is solidified at the reservoir portion. Thus, the solidified resin may be ejected at the time of a succeeding shot and mixed into a molded article. In particular, in the case of molding a transparent lens, since the solidified resin is mixed into the molded article as a foreign material, there arises a problem that the transparency of the lens degrades and a desired efficiency can not be obtained.